1. Field of the Invention
The present invention relates to a wiper apparatus.
2. Description of Related Art
A wiper arm of a wiper of a vehicle includes an urging member that urges a distal end portion of the wiper arm toward a window glass (a wiping surface) to urge a wiper blade, which wipes the window glass, toward the window glass. Specifically, the wiper arm includes an arm head and an arm member (a retainer). The arm head is fixed to a pivot shaft, which is pivoted by a drive force of a wiper motor. A base end portion of the arm member is pivotably connected to the arm head and has an inverted U-shaped cross section, which opens toward the wiping surface. A coil spring is received in the inverted U-shaped part of the arm member. The coil spring is engaged between the arm member and the arm head to urge the distal end portion of the arm member toward the wiping surface through use of, for example, a tensile force of the coil spring.
Lately, it has been demanded to further reduce the profile (a size in the height direction) of the wiper arm (wiper), for example, to improve the appearance thereof, to reduce the influences of the head wind applied thereto, and to provide an improved visibility to a driver of the vehicle. For instance, European Patent Application Publication No. EP1125806A1 discloses a wiper apparatus, in which an ordinary cylindrical spring main body of a coil spring is compressed into a generally planar form, and this coil spring is installed into an inverted U-shaped part of an arm member in such a manner that a direction perpendicular to the plane of the planar spring main body coincides with a height direction of the wiper arm. In this way, the profile of the wiper arm is advantageously reduced. Furthermore, in Japanese Unexamined Utility Model Publication No. H02-106958A, the coil spring is changed to a leaf spring to reduce the profile of the wiper arm.
However, in both of the above publications, the inverted U-shaped part of the arm member, which receives the planar coil spring or the leaf spring, needs to have the size (the thickness), which is sufficient to receive such an urging member. Therefore, the degree of freedom with respect the design of the arm member is significantly limited. Thus, it is difficult to implement the wiper arm having a good appearance suitable for modern vehicles having the high design quality. Also, it is difficult to implement the wiper arm suitable for achieving the high performance in terms of the aerodynamics to effectively urge the wiper against the wiping surface through use of the head wind.